mrbugs

Just picked up a RSB-14 and 2 minutes after powering up the sound bar, I hear a constant hum or static sound. Very noticeable when I mute it. I have reset it, tried every input. Changed HDMI cable. Tried a different wall power outlet. Makes no difference. I assume this is not normal and wondering if anyone else has experienced this. I have attached a sound file (.m4a) if interested in hearing it. Any suggestions, besides returning it? Thanks in advance. Klipsch RSB-14 humming (22JUN18).m4a